<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
		<style type="text/css">
			.box1{
				background-color: blue;
			}
			div{
				width: 500px;
				height: 500px;
				
			}
		</style>
	</head>
	<body>
		
		<!-- 
		 1.如何设置标签的背景颜色
		  background-color
		 
		 -->
		 
		 
		 <div class="box1"></div>
	</body>
</html>